The eqz numeric instruction checks if a number is equal to zero.

(module
  (import "env" "log_bool" (func $log_bool (param i32)))
  (func $main
    ;; load `0` onto the stack
    i32.const 0

    i32.eqz ;; check if the previous number on the stack is equal to 0
    call $log_bool ;; log the result
  )
  (start $main)
)

const url = "{%wasm-url%}";

function log_bool(value) {
  console.log(Boolean(value));
  // Expected output: false
}

await WebAssembly.instantiateStreaming(fetch(url), {
  env: { log_bool },
});

Syntax

value_type.eqz

• value_type

  • : The type of value the instruction is being run on. The following types support eqz:

    • i32

    • i64

  eqz

  • : The eqz instruction. Must always be included after the value_type and a period (.).

Type

[input] -> [output]

• input

  • : The input value.

  output

  • : The output value. If input is equal to 0, 1 will be pushed on to the stack, otherwise 0 will be pushed on to the stack. The output values are integers.

Binary encoding

InstructionBinary formatExample text => binaryi32.eqz0x45i32.eqz => 0x45i64.eqz0x50i64.eqz => 0x50

Specifications

Browser compatibility

See also

• eq